re #22 documentation to switch identities

docs/helpful-guides/how-to-swith-identities.md

@@ -0,0 +1,28 @@
+How to Switch Identities with a user
+====================================
+
+If you are admin, you can impersonate (switch identities with another user). This action is taken when you, as an admin, 
+needs to check the panel of a user. Whether for support or simply checking whether is using correctly your system 
+according to your terms and conditions. 
+
+The default view of this module provides the mechanism on the grid that displays the users by placing a user icon on 
+its actions column. Once, clicked, it will call the **/user/admin/switch-identity** and make the transition. Then will 
+redirect you to the index page (`goHome()`) and is there where you will have to take the correspondent actions to 
+display the views appropriated for that user. 
+ 
+How to rollback to admin user
+-----------------------------
+The way to do it is by calling that action again. The link to do that could be written like this: 
+
+```php
+$module = Yii::$app->getModule('user');
+
+if(Yii::$app->session->has($module->switchIdentitySessionKey)) {
+   echo Html::a('Switch to Admin', ['/user/admin/switch-identity'], ['data-method' => 'post']);
+}
+```
+
+Check the [switchIdentitySessionKey](../installation/configuration-options.md#switchidentitysessionkey) documentation  
+for further information regarding this configuration option. 
+
+© [2amigos](http://www.2amigos.us/) 2013-2017